Trackly is a website and a tool for tracking your weight.
Trackly can also help you plan a target weight and track your progress in achieving that goal.
Trackly is a new website, but it's under constant development, and more features are coming weekly.
Also, Trackly is completely free!

Trackly features:

Tracking your weight over time with comments.

Setting a target weight and tracking when you will reach that target.

Viewing graphs of your progress over time.

Viewing stats on your weight changes as well as tracking projected progress.

Importing your previous data into Trackly and exporting your new data as well.